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Why do we sneeze when we look at the sun?
Information
Video published by Veritasium
In this episode of Veritasium, Derek Muller explains the most recent theory about sneezing caused by looking at the sun.
To be more precise, this is mainly triggered when you come from a dark environment and look at the sun.
In short, for quite a long time, the widespread theory was that the heat of the sun made the inside of the nose sweat, which triggered a sneeze. This was refuted much later by a simple test: stepping out of a dark area, turning your face toward the sun with your eyes closed, and nothing happens.
So the newer theories involved tears flowing into the nose, or the optic nerve connecting with the nerve of the nose.
Only in the modern world has the photic sneeze reflex, also called heliotrophic sneezing, truly been analyzed and defined.
It is believed to be a genetic trait that goes very far back in human evolution. At that time, this genetic trait was an advantage.
When our ancestors lived in caves, a sneeze in the middle of the cave could spread diseases throughout the whole group. To protect us from this phenomenon, nature equipped some people with the photic sneeze reflex, to make sure they expelled their germs outside when leaving the cave and looking at the sun.
This congenital difference is said to affect nerve signals in the nucleus of the fifth cranial nerve, called the trigeminal nerve. According to some research, in some individuals this nerve is connected to the system that transmits visual impulses to the brain. So an overstimulation of the optic nerve would excite the trigeminal nerve and trigger the sneeze reflex.
So if you do not have this genetic trait, it is possible that your ancestors were not the ones living in caves :)
Why do we sneeze when we look at the sun?
Information
Video published by Veritasium
In this episode of Veritasium, Derek Muller explains the most recent theory about sneezing caused by looking at the sun.
To be more precise, this is mainly triggered when you come from a dark environment and look at the sun.
In short, for quite a long time, the widespread theory was that the heat of the sun made the inside of the nose sweat, which triggered a sneeze. This was refuted much later by a simple test: stepping out of a dark area, turning your face toward the sun with your eyes closed, and nothing happens.
So the newer theories involved tears flowing into the nose, or the optic nerve connecting with the nerve of the nose.
Only in the modern world has the photic sneeze reflex, also called heliotrophic sneezing, truly been analyzed and defined.
It is believed to be a genetic trait that goes very far back in human evolution. At that time, this genetic trait was an advantage.
When our ancestors lived in caves, a sneeze in the middle of the cave could spread diseases throughout the whole group. To protect us from this phenomenon, nature equipped some people with the photic sneeze reflex, to make sure they expelled their germs outside when leaving the cave and looking at the sun.
This congenital difference is said to affect nerve signals in the nucleus of the fifth cranial nerve, called the trigeminal nerve. According to some research, in some individuals this nerve is connected to the system that transmits visual impulses to the brain. So an overstimulation of the optic nerve would excite the trigeminal nerve and trigger the sneeze reflex.
So if you do not have this genetic trait, it is possible that your ancestors were not the ones living in caves :)
Why do we sneeze when we look at the sun?
Information
Video published by Veritasium
In this episode of Veritasium, Derek Muller explains the most recent theory about sneezing caused by looking at the sun.
To be more precise, this is mainly triggered when you come from a dark environment and look at the sun.
In short, for quite a long time, the widespread theory was that the heat of the sun made the inside of the nose sweat, which triggered a sneeze. This was refuted much later by a simple test: stepping out of a dark area, turning your face toward the sun with your eyes closed, and nothing happens.
So the newer theories involved tears flowing into the nose, or the optic nerve connecting with the nerve of the nose.
Only in the modern world has the photic sneeze reflex, also called heliotrophic sneezing, truly been analyzed and defined.
It is believed to be a genetic trait that goes very far back in human evolution. At that time, this genetic trait was an advantage.
When our ancestors lived in caves, a sneeze in the middle of the cave could spread diseases throughout the whole group. To protect us from this phenomenon, nature equipped some people with the photic sneeze reflex, to make sure they expelled their germs outside when leaving the cave and looking at the sun.
This congenital difference is said to affect nerve signals in the nucleus of the fifth cranial nerve, called the trigeminal nerve. According to some research, in some individuals this nerve is connected to the system that transmits visual impulses to the brain. So an overstimulation of the optic nerve would excite the trigeminal nerve and trigger the sneeze reflex.
So if you do not have this genetic trait, it is possible that your ancestors were not the ones living in caves :)
